The Sublayers. 11 Figure 7 Network Interface Cards. 13

 

 

 

 

 

 

 

 

 

 

 

The
Data Link Layer & Physical Layer

 

CISC530

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ASSIGNMENT 1

Qiaosheng Yu | Student ID: 217125 | Jan 30, 2018

Table of Contents
0     Introduction:
The Data Link Layer & Physical Layer. 3
1      Does the Link Layer Encapsulate
the Datagram Received from the Network Layer into a Frame?  4
2     Is the Link Layer Incapable of
Detecting an Error in a Received Frame?. 5
3      Is Flow Control One of the
Services Provided by the Link Layer?. 6
4     What Operations does the Link Layer
Support?. 6
5     A Brief Description of the IEEE
(Institute of Electrical and Electronics Engineers) 802 Standard Development. 7
6     A Brief Description of Wi-Fi
(Wireless Fidelity). 9
7     A brief Description on the Link
Layer Sublayers. 10
8     A Brief Description on NICs
(Network Interface Cards). 12
9     Types of Data Link Protocols. 13
10    MAC (Media Access Control) Design
and CRC (Cyclic Redundancy Check) Error Detection Scheme. 15
11     References. 17
 

 

Table of Figures

Figure
1 OSI Model 3

Figure
2 The Data Link Layer. 4

Figure
3 The Data Link Layer. 5

Figure
4 A Detailed List of IEEE 802 Working Groups. 8

Figure
5 Wi-Fi 9

Figure
6 Data Link Layer Sublayers. 11

Figure
7 Network Interface Cards. 13

Figure
8 Cyclic Redundancy Check. 16

 

 

0        
Introduction:
The Data Link Layer & Physical Layer

The OSI model (i.e. Open Systems Interconnection model) has
seven layers: Physical layer, Data link layer, Network layer, Transport layer, Session
layer, Presentation layer and Application layer. (OSI Model,
2018)

Figure 1 OSI Model

Source: (OSI Model, 2018)

Figure 2 The Data Link Layer

Source: (Introduction to the Data Link Layer, 2018)

 

1          
Does the Link Layer Encapsulate the Datagram Received
from the Network Layer into a Frame?

Yes.

This framing service is capable to encapsulate datagram into
a frame. A frame contains a data field, in which the datagram from the network layer
is inserted, and also several header header/trailer fields. (Data Link
Layer, 2018), (5.1 The Data Link Layer: Introduction,
Services, 2018)

Figure 3 The Data Link Layer

Source: (5.1 The Data Link Layer: Introduction, Services,
2018)

 

2         
Is the Link Layer Incapable of Detecting an Error
in a Received Frame?

No.

Data
link layer has logics to detect and recover from transmission. This can be achieved
by including a transmitting node set error detection bits into the frame and performing
an error check in the receiving node. (5.1 The Data Link Layer: Introduction, Services,
2018)

In
order to have a receiver to be able to detect transmission error, the sender
must include redundant information as an error detection code in bits form to
the frame it sent.

Upon
receiving a frame which contains an error detection code, the receiver will
recompute and try to verify if the error detection code it received can match
up with the error detection code that is previously computed. If they match then
it gets the conclusion that the frame is valid. (Data Link
Layer, 2018)

 

3         
Is Flow Control One of the Services Provided by
the Link Layer?

Yes.

Similarly to the transport layer, a link-layer protocol provides
flow control service in order to prevent the node that sends information on one
side of a link from over flowing, i.e. overloading the node that receives
information on the other side of the link. However, Data Link Layer flow
control is utilized in wireless networks and modems but not in LAN protocols
such as Ethernet. (5.1 The Data Link Layer: Introduction, Services,
2018)

 

4        
What Operations does the Link Layer Support?

The link layer supports below operations:

?    
Error Detection and Correction: as mentioned in
Part 2

?    
Flow Control: 
as mentioned in Part 3

?    
Framing and Link Access: Link Layer will
encapsulate every datagram that is received from the network layer into a
frame. MAC (i.e. Medium Access Control) protocol will be required if a single
broadcast link is been shared by multiple nodes.

?    
Reliable Delivery: this feature guarantees data transformation
across the links (for example, between two physical devices) without error. It
can be achieved with acknowledgements, error checking and retransitions and is
commonly used for links that are defined prone to high error rates.

(5.1 The Data Link Layer: Introduction, Services,
2018)

 

5         
A Brief Description of the IEEE (Institute of
Electrical and Electronics Engineers) 802 Standard Development

The IEEE (i.e. Institute of Electrical and Electronic
Engineers) is intended to improve and protect the interests of the electrical
engineering community worldwide and to establish standards for data
representation, signaling protocols and computer components. (Null & Lobur, 2003)

According to Wikipedia (IEEE 802, 2017), IEEE 802 is a
family of IEEE standards that deals with both local and metropolitan area
networks.

Figure 4 A Detailed List of IEEE 802 Working Groups

Sources: (IEEE 802, 2017)

6        
A Brief Description of Wi-Fi (Wireless Fidelity)

Now a days Wi-Fi is probably the most commonly used technology
by everyone in the world. It is a facility that allows electronic devices to be
connected to the Internet and to communicate with one another wirelessly.

It is a technology for the wireless local area to connect
and network with devices based on the IEEE 802.11 standards.  It’s a trademark of the ?Wi-Fi Alliance, which is an
international association of companies that are involved with wireless LAN products
and technologies.? (Wi-Fi, 2018)

Figure 5 Wi-Fi

Source: (Wireless Network Support, 2018)

Devices that are able to use Wi-Fi technology include
personal and commercial computers, smart phones, tablets, video game consoles,
digital cameras and audio players, smart TVs, and modern printers. Wi-Fi
compatible devices are able to connect to the public or private Internet via a
wireless access point and a WLAN.

Most commonly, Wi-Fi uses the 2.4 gigahertz (Ghz) UHF (Ultra
High Frequency) and 5.8 gigahertz (Ghz) SHF ISM (Super High Frequency Industrial,
Scientific and Medical) radio bands. By the way, these waves are very close to
the frequency that can be found in our microwave ovens. (How does Wi-Fi Work,
2015)

The Wi-Fi Alliance had used “The Standard for Wireless
Fidelity” advertising slogan for a short period of time after creating the
brand name. However, they never
officially set the name to be “Wireless Fidelity”.

Nevertheless, the Wi-Fi Alliance was also referred as the “Wireless
Fidelity Alliance Inc” in some of the publications back in those dates and the
IEEE’s official website has stated that “Wi-Fi is a short name for
Wireless Fidelity”. (Wi-Fi, 2018)

 

7         
A brief Description on the Link Layer Sublayers

The data link layer has two sub-layers: one is LLC (logical
link control sublayer) and the other one is MAC (media access control sublayer).
(Data Link Layer, 2018) (Data Link
Layer Overview, 2018)

Figure 6 Data Link Layer Sublayers

Sources: (DataLink Layer – Accessing the Media, 2018)

?    
Logical Link Control Sublayer:

Logical
Link Control Sublayer is the uppermost
sublayer which multiplexes protocols which is running at the top part of
the data link layer, and it optionally provides optionality to conduct functions such as flow
control, error notification and acknowledgment.

The
Logical Link Control Sublayer provides control and addressing function of the
data link layer. It could specify which mechanisms are going to be used for
addressing stations on top of the transmission intermediaries and for
controlling the swapped data between the originating machine and the receiving machines.
(Data Link Layer, 2018)

Which
is to say, the Logical Link Control Sublayer is managing the exchange of
information among different devices on a single link of network. This sublayer
supports several protocols to share and coexist within a multi-point physical
link layer and translated on the same network intermediary. (Data Link Layer Overview,
2018),
(Logical Link Control, 2017)

?    
Media Access Control Sublayer:

The
Media Access Control Sublayer is designed to control protocol access to the
physical network intermediaries. Via the Media Access Control addresses that
are normally given to each port on a router, different devices of one physical
link can easily identify each other at the level of data link layer uniquely.

Media
Access Control addresses are used on top of the network addresses that are
usually configured on ports within a network manually. (Data Link
Layer Overview, 2018), (Media Access Control, 2018)

 

8        
A Brief Description on NICs (Network Interface
Cards)

A Network Interface Card (Also known as network interface
controller, LAN adapter, network adapter, and physical network interface, etc.)
is a card or a circuit board that is installed in a computer. It is one of the
most important computer hardware components that can connect a computer to a
network and makes it able to send and receive information. (Network
Interface Controller, 2018)

Figure 7 Network Interface Cards

Sources: (Network Interface Controller, 2018)

A network interface
card provides a full-time connection to a network to the computer. Workstations
which are on local area networks as well as personal computers contain network
interface cards that are normally specifically designed for LAN transmission
technology. (Network Interface Card, 2006)

 

9        
Types of Data Link Protocols

Data Link protocols (also known as Layer 2 Protocols)
provide communication and interaction between devices. It is in the protocol
layer which is one level above the physical layer in relation to OSI protocol
model. There are multiple ways to connect remote devices, hence a lot of
different data link protocols exist. The defining factors will be dedicated
point to point links between devices and shared media links.

Here we introduce several most common Data Link Protocols:

?    
Synchronous Data Link Protocol (SDLC)

?    
Developed by IBM as part of its Systems Network
Architecture.

?    
Used to connect remote devices to central
computers in one-to-one or one-to-many connections.

?    
High-level Data Link Control (HDLC)  

?    
Based on SDLC, used with different interface
protocols which are defined in the physical layer.

?    
Provides a best-effort unreliable or a reliable
service.

?    
Serial Line Interface Protocol (SLIP)   

?    
A data link control facility which is used for
transmitting IP packets

?    
Rely on higher-layer protocols to perform error-detection
and correction mechanisms.

?    
Point-to-Point Protocol (PPP)   

?    
Similar but better protocol compared to SLIP
that transports both IP and other packets.

?    
Used on similar serial interfaces as HDLC.

?    
Link Access Procedure (LAP)   

?    
LAP Balanced provides one to one connections.

?    
LAP D-Channel provides control over the D
channel.

?    
LAP Frame-Mode Bearer Services provides frame
relay networks.

?    
Logical Link Control (LLC)   

?    
Defined by IEEE 802.x standards.

?    
Also used by the ANSI FDDI standard

(Data Link Protocols, 2018)

 

10     
MAC (Media Access Control) Design and CRC
(Cyclic Redundancy Check) Error Detection Scheme

MAC
(Media Access Control) design has been discussed in Part 7.

Cyclic
Redundancy Check (CRC) Error Detection Scheme is a commonly used
error-detection technique in storage devices and digital networks to check
accidental changes in raw data. It is performed based on cyclic redundancy
check (CRC) codes (also known as polynomial codes). (Introduction to the
Data Link Layer, 2018)

Cyclic
Redundancy Checks are popular because they are easy to implement and analyze
mathematically. In addition, it is particularly strong at detecting common
errors which are caused by transmission channel noises. (Cyclic Redundancy
Check, 2018)

 

Figure 8 Cyclic Redundancy Check

Sources: (Introduction to the Data Link Layer, 2018)

Referring to the above example we can see, based on the remaining
parts of a polynomial division of contents, blocks
of data get attached a short check value. Upon retrieval, it repeats the calculation
and takes corrective action on data corruption when the check values do not match.
(Cyclic Redundancy Check, 2018)

 

 

11       
References

5.1 The Data Link Layer: Introduction, Services. (2018, 1 30). Retrieved from
https://www.net.t-labs.tu-berlin.de/teaching/computer_networking/05.01.htm
Data Link Layer. (2018, 1 20). Retrieved from Wikipedia: https://en.wikipedia.org/wiki/Data_link_layer
Data Link Layer Overview. (2018, 1 30). Retrieved from
https://www.juniper.net/documentation/software/jseries/junos93/jseries-config-guide-basic/data-link-layer-overview.html
Data Link Protocols. (2018, 1 30). Retrieved from
http://www.linktionary.com/d/data_link.html
DataLink Layer – Accessing the Media. (2018, 1 30). Retrieved from
http://www.highteck.net/EN/DataLink/Data_Link_Layer.html
How does Wi-Fi Work. (2015, 7 15). Retrieved from Scientific American:
https://www.scientificamerican.com/article/how-does-wi-fi-work/
IEEE 802.
(2017, 12 4). Retrieved from Wikipedia:
https://en.wikipedia.org/wiki/IEEE_802
Introduction to the Data Link Layer. (2018, 1 30). Retrieved from
http://www.science.smith.edu/~jcardell/Courses/EGR328/Readings/KRch5Link.pdf
Logical Link Control. (2017, 4 29). Retrieved from Wikipedia:
https://en.wikipedia.org/wiki/Logical_link_control
Media Access Control. (2018, 1 29). Retrieved from Wikipedia:
https://en.wikipedia.org/wiki/Medium_access_control
Network Interface Card. (2006, 8 1). Retrieved from
http://searchnetworking.techtarget.com/definition/network-interface-card
Network Interface Controller. (2018, 1 29). Retrieved from Wikipedia:
https://en.wikipedia.org/wiki/Network_interface_controller
Null, L., & Lobur, J. (2003). The Essentials
of Computer Organization and Architecture. Sudbury, Massachusetts: Jones
and Bartlett Publishers, Inc.
OSI Model.
(2018, 1 21). Retrieved from Wikipedia:
https://en.wikipedia.org/wiki/OSI_model
Wi-Fi.
(2018, 1 19). Retrieved from Wikipedia: https://en.wikipedia.org/wiki/Wi-Fi
Wireless Network Support. (2018, 1 30). Retrieved from

Wireless Network Support


 

 

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